Since 1,2-polybutadiene having a suitably controllable crystallinity comprises a crystalline part and an amorphous part, and has a carbon—carbon double bond has a high chemical reactivity in a molecule, it has not only the function as a thermoplastic elastomer but also the function as the conventional vulcanized rubber and a thermosetting resin having the high cross-linking density. In addition, since this 1,2-polybutadiene is excellent in a processibility, it is applied as a modifier for other resins and thermoplastic elastomers, or a medical polymer material.
Conventionally, 1,2-polybutadiene having a controlled crystallinity has been obtained by using a catalyst comprising a cobalt salt phosphine complex, trialkylaluminium and water (JP-B-44-32425), or a catalyst comprising a cobalt compound, trialkylaluminium, water and a triphenylphosphine derivative (JP-B-61-27402). These catalytic systems show a high polymerization activity in a halogenated hydrocarbon solvent, such as methylene chloride, and has reduced polymerization activity in a hydrocarbon solvent, therefore, polymerization is performed by using a halogenated hydrocarbon solvent.
However, since 1,2-polybutadiene polymerized using a halogenated hydrocarbon solvent contains a considerable high amount of halogen such as chlorine and the like due to the solvent remaining therein, hydrogen halide such as hydrogen chloride is generated at high temperature molding, there arises problems that a mold is rusted, 1,2-polybutadiene is thermally deteriorated and the physical properties are changed with time.
Further, it is requested that 1,2-polybutadiene has more excellent properties as a thermoplastic elastomer.
An object of the present invention is to provide 1,2-polybutadiene which does not cause the mold contamination and the thermal deterioration at high temperature molding and has improved change with time in the physical properties, and a thermoplastic elastomer composition excellent in the moldability, the transparency, the mechanical strength and the wet skid resistance.